Deformation-induced atomic rearrangements and crystallization in the shear bands of a Tb75Fe25 nanoglass

Abstract

Tb75Fe25 nanoglass samples were prepared by cold pressing amorphous nanoparticles (produced by the inert gas condensation method). One of the bulk nanoglass samples was severely plastically deformed using high-pressure torsion. The structure of the deformed and non-deformed nanoglass samples was examined by X-ray diffraction. Differential scanning calorimetry of the samples showed a higher thermal stability of the non-deformed sample when compared to the severely plastically deformed sample. The results suggest a more relaxed structure being present in the non-deformed sample as compared to that of the deformed sample. Transmission electron microscopy performed on the deformed sample revealed the presence of shear band-like features with indications of crystalline terbium precipitates. Atom probe tomography was used to identify compositional changes in both the non-deformed and the deformed samples. The non-deformed structure showed a homogeneous distribution of both Tb and Fe, whereas a terbium enhancement (up to 90%) was observed within the shear bands of the deformed sample. The Tb segregation and crystallization within the shear bands observed both by electron microscopy and atom probe tomography are clear indications of the structural changes occurring in the shear band regions during the deformation. It is concluded that the diffusion is enhanced leading to the compositional variation within the shear bands.